Projection surface

ABSTRACT

A projection surface for the viewing of a projected video image or equivalent has a reflective surface of the projection surface. The reflective surface has color elements of at least three colors, arranged side by side on the projection surface so as to cover the entire reflective surface of the projection surface.

This application is the national phase under 35 U.S.C. § 371 of PCTInternational Application No. PCT/FI01/01061 which has an Internationalfiling date of Dec. 7, 2001, which designated the United States ofAmerica.

FIELD OF THE INVENTION

The present invention relates to a projection surface designed forimages projected such as by a video projector or equivalent.

DESCRIPTION OF BACKGROUND ART

Prior-art solutions for a similar purpose include textile projectionscreens with a reflective surface having a white basic color, thusreflecting all colors. In large spaces and for purposes requiring alarge angle of view, projection screens with a dull finish, which aregood general-purpose screens, are often used. However, theirreflectivity is relatively poor for demanding applications, andtherefore they are not well suited for use in bright spaces where thereis plenty of diffused light. Metal-coated aluminum or silver screens andso-called iridescent screens give a better reflectivity than dullprojection screens, but the problem is a much narrower angle of view. Amajor problem in the case of all the projection screens described aboveis encountered in the projection of a dark or completely black coloronto the light or white surface of the projection screen. Black portionsin the image are areas on which no light is projected at all. All video,motion-picture and slide shows generally look fine in conditions ofcomplete darkness, but when any extra light is admitted into the viewingspace, dark portions in the projected image assume a lighter appearance.This extra light is generally called diffused light. The larger theamount of diffused light admitted, the whiter do the dark portionsappear, and the image seems to loose contrast. Even in a completely darkroom, diffused light is produced when the image is projected onto awhite surface. Therefore, on a prior-art projection screen, the imagehas a poor contrast because black portions of the image are the samecolor with the white screen. In spaces containing diffused light, normalcontrast is achieved by increasing the brightness of the image, whichagain causes strain of spectators' eyes while also producing morediffused light, thus further weakening the contrast.

A solution disclosed in U.S. Pat. No. 5,864,426 aims at improving colordistribution in a projected video image by increasing the reflection ofthe blue light component. This is implemented by providing the screenwith blue reflective elements placed at even distances among the whitestandard reflective elements, thus improving the reflection of bluelight and correspondingly reducing the reflection of red and greenlight. This solution, too, has the drawback that, while producing abright image with a good color distribution, it cannot produce the blackportions of the image correctly. Since most of the reflective elementsin this projection screen, too, are white, black portions of the videoimage mainly look white.

U.S. Pat. No. 5,193,015 also discloses a solution dealing with theproblem caused by diffused light. It comprises a reflector elementconsisting of a number of superposed layers, two of which are designedto reflect red color, two to reflect green color and two to reflect bluecolor. The reflector element additionally contains other layers. Thesolution disclosed in this patent is actually not a textile projectionscreen but a liquid crystal operated reflector element, which is veryexpensive as compared with a textile projection screen, especially whenimplemented in a large size. In addition, a reflector element of thistype is considerably more susceptible to damage than the projectionsurface of the present invention, which may be e.g. a textile projectionscreen or equivalent.

BRIEF SUMMARY OF INVENTION

The object of the present invention is to eliminate the above-mentioneddisadvantages and to achieve a projection surface for use in a textileprojection screen or equivalent that is better than prior-art solutionsand has good brightness and contrast properties and is capable ofreflecting dark portions of the image better than prior-art solutions,especially when the viewing space contains diffused light causing aweakening of contrast. Thus, the projection surface of the invention isexcellently applicable for use e.g. in large public spaces requiring awide angle of view and, due to extra light, a good contrast. A furtherobject is to achieve an economical and reliable solution that is assimple, durable and functional as possible for use in place of currenteasy-to-use projection screens.

The solution of the invention provides the advantage that, by enhancingthe dark portions of the image, it makes it possible to produce an imagewith a contrast multiple times better than in current projected images,an image that has an excellent quality even when the viewing spacecontains diffused light. Another advantage is that the tonal value ofthe image can be maintained even in a space with some illumination.Moreover, the image has a good color distribution. An additionaladvantage is that the projection surface of the invention can beproduced at a low cost as the structure of the projection surface isrelatively simple.

Further scope of the applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWING

In the following, the invention will be described in detail by the aidof an example embodiment with reference to the attached drawing, whichis given by way of illustration only, and thus is not limitative of thepresent invention, and wherein:

FIG. 1 presents the solution of the invention in an oblique front view.

DETAILED DESCRIPTION OF THE INVENTION

The projection surface 1 of the invention has a structure that differsfrom prior-art solutions in that it has no white surface at all, amongother things. The projection surface consists of adjacent colored spotsserving as color elements, which are all of equal size and spaced ateven distances on the surface. Each individual spot is monochromatic.The spots are colored red, green and blue, i.e. with the so-called RGBcolors. The spots are so arranged that, on a horizontal row, there isfirst a red spot 2, and next to this without an interspace a green spot3, and similarly next to this a blue point 4, likewise without aninterspace. After the blue spot there is again a red spot, and so on.The next row below the first one correspondingly starts with a blue spot4, which is followed by a red spot and a green spot. The next row belowthat starts with a green spot, correspondingly followed by a blue spotand a red spot. No interspaces are left between rows, either. The entireeffective area of the projection surface has been prepared with thisarrangement of colored spots, and consequently the surface is not of alight color but appears to be dark gray when seen from a distance.

The colored spots can be created on the projection surface by a knowntechnique. They may be created by spraying in tiny drops, by a printingpress technique or by printing on a suitable device, or they may becreated by weaving the projection screen from yarns of the requiredcolors. The essential things are even spacing and equal size of allspots as far as possible. The spots need not necessarily be very small,because on a large projection surface and when viewed from a longdistance, they combine as a dark gray hue even if they are relativelylarge. This facilitates the task of producing the projection surface asfar as the colored spots are concerned.

The shape of the colored spots may vary depending on the method ofmanufacture of the projection surface. A good shape is that of a squareor rectangle, in which case no gaps are left between separate spots. Ifthe projection surface consists of a woven fabric, then the shape of thecolored spots depends on the weaving method and the yarns used.

A video projector generally transmits red, green and blue light rays,which are so applied to the projection surface that a polychrome imageis produced, which is reflected from the surface to the spectators. Theprojection surface of the invention is excellently applicable for usewith a video projector because the color elements on the surface areexactly the same colors as those transmitted by the video projector.However, this does not mean that the projection surface cannot be usedwith a slide projector or film projector or in a presentation of coloredor black-and-white transparencies. The projection surface of theinvention is just as well suited for these uses, producing a brightimage with a good contrast.

It is obvious to the person skilled in the art that the invention is notlimited to the example described above, but that it may be varied withinthe scope of the claims presented below. Thus, the structure of theprojection surface may differ from the structure described above e.g. inthat the colored spots are arranged in a different way than in the abovedescription. Spots of different color may be placed side by side in thehorizontal direction, but in the vertical direction spots of the samecolor may be placed one above the other. Moreover, the structure maydiffer in that it does not contain equal quantities of all three colors;instead, depending on the required applicability, the quantity of agiven color may be larger or smaller than that of the other two colors.This may be implemented either as a larger or smaller number of coloredspots or by using colored spots of a larger or smaller size. A furtherpossibility is that the numbers or sizes of spots of each differentcolor are different. In addition, it is possible to use another,additional color besides the aforesaid three colors.

The solution of the invention concerns a projection surface which may bemade of any material suited for use as a surface material. It isconceivable, for example, that the projection surface, either in itselfor together with a suitable backing material attached to it, forms anassembly that can be called a projection screen.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

1. Projection surface for the viewing of a projected image, such as avideo image or equivalent, where the surface of the projection surfaceconsists of the combination of color elements of several colors, thecolors of the color elements have been chosen to correspond to thecolors produced by the projector in use, the color elements consist ofdifferently colored yarns or equivalent, from which the reflectivesurface of the projection surface has been woven, the projection surfacehas been woven from yarns which have been twisted of yarns of severalcolors.
 2. A projection surface for viewing of a projected image where asurface of the projected surface includes a combination of colorelements of several colors, the colors of the color elements beingchosen to enhance dark portions of the projected image and to correspondto colors produced by the projector in use, the projector surface havingat least three colors arranged alternately side by side in bothhorizontal and vertical directions so as to cover the projection surfacein a way that the projection surface appears to be dark gray when seenfrom a distance.
 3. The projection surface as defined in claim 2,wherein an entire surface of the projection surface is covered by the atleast three colors.
 4. The projection surface as defined in claim 2,wherein the at least three colors comprise three colors and are the onlycolors on the projection surface.
 5. The projection surface as definedin claim 2, wherein the color elements are of substantially equal sizeand are of red, green and blue color and wherein the color elementscontact one another.
 6. The projection surface as defined in claim 5,wherein the three colors are the only colors on the projection surface.7. The projection surface as defined in claim 2, wherein the colorelements are relatively small in relation to a size of the projectionsurface and cover an entire surface of the projection surface evenly inboth horizontal and vertical directions so that, in the horizontaldirection, a red element is always followed by a green element, a greenelement by a blue element and a blue element again by a red element, andthat in the vertical direction, a red element is followed by a blueelement, a blue element by a green element and a green element again bya red element.
 8. The projection surface as defined in claim 2, whereinthe colors are arranged as straight lines and have been placed side byside close to each other.
 9. The projection surface as defined in claim2, wherein the color elements have been created on a reflective surfaceof the projection surface by one of painting, a printing press techniqueor printing on a printer.
 10. The projection surface as defined in claim2, wherein the color elements are differently colored yarns from whichthe projection surface has been woven.
 11. The projection surface asdefined in claim 10, wherein the projection surface is woven from theyarns which are twisted yarns of several colors.
 12. The projectionsurface as defined in claim 10, wherein only red, green and blue colorsare on the projection surface.
 13. The projection surface as defined inclaim 2, wherein the color elements are in a single plane.
 14. Theprojection surface as defined in claim 13, wherein only three colors areused for the color elements, the color elements cover the entireprojection surface.
 15. The projection surface as defined in claim 14,wherein the color elements are arranged with at least three sides, eachof the sides of the color elements contacting an adjacent side ofanother color element.
 16. The projection surface as defined in claim15, wherein the color elements have four sides, the color elements beingarranged in straight lines in both horizontal and vertical directions onthe projection surface.
 17. The projection surface as defined in claim2, wherein the color elements are arranged with at least three sides,each side of the color elements contacting an adjacent side of anothercolor element.
 18. The projection surface as defined in claim 17,wherein adjacent color elements contact one another along a completelength of the sides of the color elements.
 19. The projection surface asdefined in claim 2, wherein the color elements have four sides, thecolor elements being arranged in lines in both horizontal and verticaldirections on the projection surface.